Original Manual: ftp://ftp.zyxel.com/P-660HN-51/user_guide/P-660HN-51_1.1_ed1.pdf
Step 1: Type the IP address 192.168.1.1 in your browsers address bar, then log in as an admin.
Step 2: Click on Network Settings -> Broadband to open your existing connections, the click on the pen and paper icon under Modify
Step 3: On the next page, scroll down until you see DNS Server. Set the DNS to STATIC and enter the IP addresses:
- 208.67.222.222
- 208.67.220.220
Step 4: To ensure that OpenDNS is working properly for you, please flush your browser and DNS cache by following the instructions below:
http://www.opendns.com/support/article/67
http://www.opendns.com/support/article/68